Type bar impact control



Dec. 5, 1961 A. w. SCRIBNER 3,011,616

TYPE BAR IMPACT CONTROL Filed Sept. 30, 1960 2 Sheets-Sheet 1 REQUIRED SPEED Ar 10 11 F] cu'r OFFTO GIVE A DESIRED spasm AT A mPAc'r OF A GIVEN TYPE BAR.

l l 1 I l I DEGREES (9) FROM HEADREST Fig.2

INVENTOR ALBERT W. SCRIB R aa-W44 M ATTORNEY De'c. 5, 1961 A. w. SCRIBNER 3,0

TYPE BAR IMPACT CONTROL Filed Sept. 30, 1960 2 Sheets-Sheet 2 I I I TI 4 I I I I I I l I I I I l l I I I I I INVENTOR ATTORNEY,

ALBERT W. SCRIBNE.

United States Patent 3,011,616 TYPE BAR IMPACT CONTROL Albert W. Scribner, West Hartford, Conn., assignor to Royal McBee Corporation, Port Chester, N.Y., a corporation of New York Filed Sept. 30, 1960, Ser. No. 59,773 11 Claims. (Cl. 197-17) This invention relates to a novel type action and more specifically relates to a novel method and arrangement for controlling the printing impact of a type bar of an electric typewriter.

In order to obtain good print work from a typewriter it is essential that any given type bar in the machine always strike the platen with a predetermined and substantially uniform impact during repeated typing operations. If the successive typing impacts of any given bar vary then the typed characters appearing on the record sheet will be correspondingly light and dark in shade intensity.

In the usual electric typewriter action a type bar which is to efiect a printing operation is displaced through approximately 90 degrees in moving from the head rest to the platen. The first portion of this displacement comprises a power stroke during which the type bar is accelerated as a result of being efiectively coupled to a power roll or a similar driving means. At some point in the latter part of the type bar displacement a power cut ofi is effected, i.e. the type bar is eifectively uncoupled from the power roll and the bar together with the immediately related parts of the action are thereafter allowed to move in substantially free flight until printing impact occurs. During =free flight the type bar is decelerated due primarily to the action of the type bar return spring or springs, and to a lesser degree by the frictional drag acting on the various moving parts of the type action. Under these general dynamic conditions when power cut off is efiected relatively early in the type bar displacement the time period allocated for type bar acceleration is decreased, while the period permitted for type bar deceleration is increased. Conversely when power cut off is efiected relatively late in the type bar displacement the length of the power stroke and hence the type bar acceleration period is increased while the free flight stroke and hence the deceleration period is decreased. As will be apparent not only is the point of power cut off important in the determination of the final printing speed possessed by the type bar as it strikes the platen but the intensity of the print work produced by a given type bar will normally be very sensitive to any deviation of the actual power cut off point from the predetermined desired cut ofl point for that particular type bar.

In the operation of conventional type actions it has been assumed that the type bar acceleration characteristics during repeated power strokes of a given bar are substantially uniform and hence that the respective speeds of the bar at its various respective angular positions during these repeated power strokes are also substantially uniform. Based on this assumption the power cut 0E for each type bar is located at a predetermined point along the displacement path of the type action. Here for example, adjustable power cut-cit set screws are sometimes used to effect a disengagement of a roll cam from a power roll after the type bar has been power driven to a predetermined angular position. The dithculty encountered in this type of arrangement is that the acceleration characteristics of a given type bar during repeated typing operations are not always uniform to the degree required to avoid the above noted light-dark printing problem. Here, when the type bar reaches any predetermined angular position in its power stroke its ice speed may be above or below that anticipated by reason of the effects of certain operational variables such as the point where the roll cam and power roll are efiectively coupled, backlash between the type action parts, slippage in the drive connections, variations in power roll speeds, etc. As a result if the power cut off occurs at a normally fixed position and it the speed of the type bar when it reaches this position varies depending on the effects of said variables it will be apparent that the typing impact and print intensity produced by successive actuation of a given type bar will also Vary thus giving poor print work.

The present invention is concerned with controlling the power cut-ofi to a type bar by taking into consideration not just the arrival of the type bar to a predetermined angular position, but the combined effects of both type bar position and speed in such a way that the above mentioned type bar drive variables which at present are at least partially determinative of the accelerational characteristics of the type action, are no longer operative to variably effect the intensity of the printing impact of the type bar.

One object of the invention is to provide a novel type bar speed contro arrangement for typewriters wherein means are provided for sensing when, during an given typing cycle, the type bar has reached any one of a predetermined set of critical combined conditions of. speed and position.

Another object of the invention is to provide a novel type bar speed control arrangement for typewriters whereby for each typing cycle or operation the typing impact is controlled by sensing the speed of the type bar during its power stroke and efiecting a power cut ofi thereto during said cycle in accordance with the speed measurements made.

Another object of the invention is to provide a novel type action wherein a power cut off to the type bar is effected whenever the speed and position of the bar matches any one of many difierent predetermined desired tree flight conditions of speed and position for that particular type bar.

Another object of the invention is to provide a novel type action whereby the speed of the type bar is sensed during the power stroke and whereby power cut off is eflected when the type bar reaches a predetermined desired speed at a predetermined desired angular position.

Another object of the invention is to provide a novel method and apparatus for controlling the speed of a type bar whereby the driving of the type bar is terminated when a predetermined desired set of dynamic conditions have been reached which will give the desired free flight typing impact after the predetermined type bar decelerating forces have been overcome.

Another object of the invention is to provide a novel method of controlling type bar printing impact whereby the decelerating effects on any given type bar of the type bar return spring and other factors such as frictional drag are measured so that the type bar free flight speeds required at positions of varying distances from the platen to respectively produce an acceptable typing impact may be determined, and whereby the power to the type bar is cut off when the type bar reaches one of the several predetermined desired free flight conditions of speed and position.

Another object of the invention is to provide a type action having a centrifugally sensitive fly weight for sensing the speed of the type bar and controlling the driving action for the latter so that it will possess a predetermined desired speed at pr nting impact.

Still another object of the invention is to provide a novel type car speed control apparatus wherein a centrifugally sensitive fly weight senses the speed of the type action during a power stroke, said fly weight being engageable at various points along one predetermined surface of an element which when displaced serves to cause disengagement of the type action from its drive means.

A further object of the invention is to provide a novel power cut off for an electric typewriter whereby a type action may be automatically uncoupled from an asso ciated power roll at different points during successive power strokes of the type bar while substantially uniform intensity to the printing work is still retained.

Other objects and many of the attendant advantage of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings in which like reference numerals designate like parts throughout the figures thereof and wherein:

FIGURES l and 2 are graphs illustrating the operational concept of the instant invention.

FiGURE 3 is a side elevational view illustrating the construction and arrangement of the instant type bar speed control apparatus.

FIGURE 4 is an exploded perspective view of some of the apparatus shown in FIGURE 3.

FIGURE 5 is afragmentary front elevational view illustrating the lower end construction of the various sub levers of the typewriter.

FIGURE 6 is an active view of the parts shown in FIGURE 3.

After the power cut-ofl? of a driven type bar has been effected the free flight of the bar is opposed and slowed down principally by the action of the type bar return spring or springs, and to a much lesser degree by the frictional drag of the various parts of the moving type action. If a particular impact speed of the type bar is desired then the type bar must be initially driven to a higher maximum speed so that after cut-off the predetermined eifects of the above mentioned spring and frictional decelerating forces will cause the type bar to slow down to said particular desired terminal or impact speed.

Referring to FIGURE 1 the line 10 represents the free flight speeds '(S) of the type bar at various positions which are required to overcome the decelerating action of the type bar return spring in order. that the type bar have a desired terminal speed of S Superimposed with respect to line 10 is a curve 11 which illustrates the added deceleration effects of the average frictional drag of the various parts of the moving type action over and above the effects noted by line it In that the actual values represented by line it may be quite accurately determined for any given bar and its return spring, and

in that a fairly accurate average value may be determined fo'rthe much smaller frictional decelerating effects, the combined deceleration effects represented by curve 11 may be determined and plotted for any given type bar with a workable degree of accuracy, and this dynamic operation of the type bar will inherently be substantially uniform for each successive typing operation of the bar; curve 11 indicatingthe free flight type bar speeds at various angular positions required to give the said type bar its final desired printing speed S at the time of impact.

The curve 11 is again illustrated in FIGURE 2 together with an exemplary curve 12 which illustrates the speed changes of the type bar as the latter is accelerated by the power roll during a power stroke. If the power stroke 13 is here coutinueduntil the curve 12 intersects the curve 11 as at 14 and a power cut off is effected at that time, then the type bar will cont'mue to move through a :free flight stroke 15 in accordance with the predetermined and predictable conditions noted by the remainder of curve 11 so that a predetermined typing speed S will result at printing impact. If the next power stroke of the samegtype bar follows the different dynamic conditions exemplified by curve 16 then cut-elf should be cffected at the intersection point 17 so that the type bar may again follow the inherent predictable dynamic conditions noted by curve 11 to effect a printing impact having the same intensity as in the previous typing operation of the bar. As will be apparent no matter what the acceleration characteristics of the type bar are during its power stroke, eg that noted by curves 12, 16 or 20, as soon as the conditions of both speed and position of the type bar match any point on the substantially fixed curve 11 a power cut off should be effected so that the free flight of the bar will be allowed to follow the substantially fixed inherent operational characteristics of motion as represented by the remainder of curve 11. In this way the printing impact of the type bar will always be substantially the same and hence the printed characters will be uniform in shade or intensity.

Apparatus is provided for sensing the critical conditions of both speed and position of each type bar during each of its power strokes. Referring to FIGURE 3 there is shown a conventional type rubber roll action comprising a sublever 30 which is pivotally mounted on the cross shaft 31 and which is biased to a normal counter clockwise position by a type bar return spring 32. A roll cam 33 is pivotally mounted on the sublever by means of a stud 34 and is rotatably biased to a normal counter clockwise position by means of a spring 35. The roughened eccentric peripheral surface 36 of the roll cam is adapted to be swung into operative engagement with the periphery of a continuously driven rubber coated power roll 37 by means of a suitable key action acting on the roll cam tail 41 as diagrammatically illustrated at 40 in FIGURE 3. As the roll cam surface 36 progressively engages the power roll periphery the sublever 30 is driven through a clockwise power stroke so as to correspondingly swing the related type bar towards the platen. The construction and operation of this type of drive unit is well known in the art and further explanation thereof need not be made here. Sufice it to say herethat at some point in the clockwise power stroke of sublever 30 the roll cam 33 is caused to be disengaged from the power roll 37 to effect a power cut-oif to the type bar so that the latter may continue its motion in free flight to the printing point of the typewriter.

The above described type action which is exemplary of the various other type actions in the machine is augmented as follows. The sublever 30 is provided with a depending projection 42, FIGURES 3, 4 and 5, on which is slidably mounted a small apertured centrifugally sensitive fly weight 43. The weight 43 isnormally biased into engagement with the bent off sublever pin 44, FIG- URE 5, by means of a spring 45 that is anchored to the upper portion of the sublever projection 42. Pivotally mounted on said sublever supporting cross shaft 31 is a bail 46 which is biased into normal engagement with the frame stud 47 by means of a very light spring 48. The body portion 49 of the bail defines a comb having a plurality of forwardly extending teeth 50, FIGURE 4, which are respectively associated with the various type actions of the machine. 'The comb tooth 50a associated with the said sublever 30 extends laterally adjacent the sublever projection 42 and slightly below the lower side edge of the normally positioned fly weight 43 as is best illustrated in FIGURES 4 and 5. As will be apparent when the sublever 30 is power operated as above described the fly weight 43 will, due to centrifugal force, move radially outwardly 51, FIGURE 3, along the sublever projection 42 and against the action of spring 45 as the sublever swings in. a clockwise direction through various angular positions illustrated at 52 of FIGURE 3 and will engage the upper edge 53 of the comb tooth 50a. For a given mass of the fly weight 43 and a given spring constant for spring 45 the radial positions of fly weight 43 along the sublever projection 42 will be determinable or predictable for the various diiferent'pivotal speeds of the sublever 30 on the cross shaft, 31., In view of this the said upper edge 53 of comb 50a is contoured and positioned so that the radial distances between said edge and the axis of the sublever pivot shaft 31 for the respective successive rotary positions 52 of the pivoting sublever 30 correspond to the conditions noted by the said curve 11 of FIGURE 2, i.e. for any given position and speed of the driven sublever 30, corresponding to a given point on the curve 11, the fly weight will be just making contact with the comb tooth edge 53. Under these conditions it will be apparent that when the fly weight 43 engages any point along the upper surface 53 of the comb tooth the dynamic conditions of both speed and position as represented by some point on curve 11 have been attained by the type bar and if a power cut 011? can be effected immediately the type bar can complete its printing stroke in free flight in the inherently uniform manner designated by the remainder of said curve 11.

Means are provided for automatically causing disengagement of the roll cam 33 from the power roll 37 in response to the engagement of fly weight 43 with the bail tooth edge 53. The right hand end, FIGURE 4, of bail 46 is formed with a forwardly extending arm 55 to which is connected a flexible cantilevered leaf spring 56. The forward bent off end 57 of this leaf spring extends upwardly between two studs 58 and 59 provided on a locking cam 60. The cam 60 is pivotally mounted on the machine side frames by means of a stud shaft 61 and is formed with a roughened and slightly eccentric peripheral surface 62. In the normal position of bail 46 the bent ofi end 57 of the leaf spring lightly engages the cam stud 58 so as to bias the locking cam 60 into normal engagement with a frame stud 63. A cross shaft 65 is pivotally mounted in the machine side frames and has fixed thereto an elongated rearwardly extending power cut off bail 66 which is normally disposed a short distance below the various roll cam tails such as 41. The bail 66 is biased into normal engagement with a frame stud 67 by means of a spring 70. Also fixed on cross shaft 65 is a rubber coated locking disc or roll 71 having a lower portion of its periphery disposed immediately above the surface 62 of the locking cam 60.

The above described apparatus defines a means for permitting a power cut oif point to be selected at a time after the power stroke of the type bar has started, and for automatically uncoupling the type action from the power roll at varying points during the respective successive power strokes of the type bar so as to give uniform impression for that particular type bar.

The normal condition of the-parts described is shown in FIGURES 3-5. In operation when the roll cam 33 becomes engaged with the power roll 37 the roll cam tail 41 will spring downwardly during the ensuing power stroke and will immediately engage and correspondingly displace the bail 66. As the bail 66 thus follows the downward movement of the roll cam tail 41 the locking disc or roll 71 will partake of a rotary motion. As the sublever 30 is being driven in a clockwise direction the fly weight 43 will tend to move radially outward against the action of spring 45 due to the centrifugal forces set up. The arcuately moving fly weight 43 will thus ultimately engage and slightly pivotally displace the bail 46 which will cause the bail arm 55 and leaf spring 56 to move through a very short downward stroke. Immediately at the beginning of this stroke the locking earn 60 will be swung into operative engagement with the periphery of the now rotating locking disc 71 thereby arresting the rotary motion of disc 71 as well as the downward movement of bail 66 and the roll cam 33 as illustrated in FIGURE 6. This action causes the disengagement of the roll cam from the power roll and hence effects a power cut off to the type bar being driven. The following free flight movement of the parts is accommodated by the slight flexing of leaf spring 56 while the roll cam 33 is immediately restored to its normal position relative to the sublever 30 by the action of the spring 35 and the bail 66 is restored to its normal position by spring 70. At typing impact the sublever 30 will stop moving momentarily and the fly weight 43 will tend to move upwardly under the action of its spring 45 thus freeing bail 46 for movement to its normal position by the action of spring 48. Bail 46 is thus free to accommodate a subsequent typing operation which may or may not be chronologically overlapped with the previous typing operation. After typing a character on the record sheet the type bar together with the remaining parts of the action will be restored to their normal positions shown in FIG- URE 3. During the successive typing operations the length of the power stroke will vary depending on the acceleration characteristics of the type bar motion. It will be noted from FIGURE 2 that when the power stroke is relatively long the maximum required speed is less than when the power stroke is relatively short.

It will be apparent from the above discussion that a power cut oti to the actuated type bar will occur only when the dynamic conditions represented by a point on the curve 11, FIGURE 2, have been attained. These conditions may occur relatively early or late in a power stroke and hence there is no fixed angular position of the type bar when out off is affected during each successive operation of the bar; rather cut off occurs only when both the speed and position of the type bar has reached any one of many different predetermined combination of values. Under these conditions the successive typing impacts of said bar will always be substantially the same and hence it is immaterial to the print work whether the type bar acceleration was slow or fast, whether the power roll and roll cam engagement was early or late, whether there was slippage in the driving action, etc. Here the unpredictable effects of all the variables which go into the driving of the type bar will no longer aflect the printing impact because the operational datum used for determining the substantially uniform successive impacts of a given type bar is based on the inherently uniform decelerating conditions acting on the type bar rather than on the relatively unpredictable accelerating conditions acting thereon.

As will be understood the various other type actions of the typewriter are constructed and will operate in a manner similar to that for the action just described, the various upper edges, corresponding to 53, ofthe respective comb teeth 50 being respectively contoured and positioned so as to give the desired impact for the respectively associated type bars.

While there is in this application specifically described one form which the invention may assume in practice, it will be understood that this form of the same is shown for purposes of illustration only and that the invention may be modified and embodied in various other forms without departing from its spirit or the scope of the appended claims.

The invention claimed is:

l. A method of controlling the printing impact of a given type bar; comprising the steps of determining at positions located at different distances from the typewriter printing point the various free flight speeds required of the type bar to give a desired printing impact against the action of the decelerating forces experienced by the type bar during said free flight, driving said type bar from a normal rest position towards said printing point, sensing the speeds of said type bar as it is being driven, and terminating the driving of said type bar when the dynamic conditions of speed and position of the driven bar match any one of the said determined free flight conditions of speed and position of the type bar whereby the predetermined and predictable free flight conditions of said type bar essentially determine the uniformity of intensity of the respective successive printing impacts rather than the relatively unpredictable conditions of the respective power driven strokes thereof.

2. In a printing machine having at least one movably mounted printing element, drive means for actuating said printing element, means for effectively coupling said printing element to said drive means, and means for effec tively uncoupling said printing element from said drive means; the improvement comprising means for sensing the speed of said printing element during the time that said printing element is effectively coupled to said drive means, and means responsive to the operation of said speed sensing means for causing operation of said means for effectively uncoupling said printing element from said drive means before a printing action occurs.

3. In a typewriter; a type bar adapted to be moved from a rest position to a printing position, a power drive means, means for eflfectively coupling said type bar to said power drive means, means for effectively uncoupling said type bar from said power drive means at a selected one of many diiferent positions of said type bar during its printing stroke, and means operative during a given printing stroke of said type bar for determining a desired one of said positions and for causing operation of said uncoupling means when said type bar is at said determined position prior to the completion of said given printing stroke.

4. In a typewriter; a type bar adapted to be moved from a rest position to a printing position, a power drive means, means for effectively coupling said type bar to said drive means, means capable of effectively uncoupling said type bar from said power drive means at any one of several desired times during any given power stroke of the type bar, means for determining when said uncoupling means should be operated, and means responsive to the operation of said last mentioned means for operating said uncoupling means during the respective typing strokes.

5. In a typewriter; a type bar adapted to be moved from a rest position to a printing position, a power drive means,

means for etfectively coupling said type bar to said power drive means, means for elfectively uncoupling said type bar from said power roll at any point during a power stroke of the type bar, and means for automatically operating said uncoupling means at various points during the respective successive power strokes of said type bar.

6. In a typewriter; a type bar adapted to be moved from a rest position to a printing position, a power drive means, means for effectively coupling said type bar to said power drive means, means for effectively uncoupling said type bar from said power drive means, and means conditionable in response to a power stroke of the type bar for controlling the operation of said uncoupling means so as to terminate said power stroke.

7. In a typewriter having at least one type bar, a drive .means, means for effectively coupling said type bar to said drive means, and means for effectively uncoupling said type bar fromsaid drive means; the improvement comprising means for sensing the arrival of said type bar at any one of a plurality of predetermined sets of dynamic conditions of both speed and position, and means operated by said sensing means for operating said means 8 for effectively uncoupling said type bar from said drive means.

'8. In a typewriter having a type bar, a power drive means, and means for eifectively coupling said type bar to said power drive means, the free flight speeds of said type bar required at positions located different distances from the typewriter printing point to give a predetermined printing impact against the action of the measured inherent type bar decelerating forces being measured and known; the improvement comprising means for efiectively disengaging said type bar from said power drive means, means for sensing when the dynamic condition of the driven type bar matches any one of the said known speedposition conditions for free flight of said type bar, and means responsive to the operation of said sensing means for operating said means for effectively uncoupling said type bar from said power roll whereby said type bar printing impact will always be substantially uniform.

9. In a type action having at least one type bar, a drive means, and means for etfectively coupling said type bar to said drive means; the improvement comprising means for effectively uncoupling said type bar from said drive means, a fly weight connected for movement in timed relation with said type bar and yieldably supported on the type action so as to be centrifugally sensitive to the speed of movement of said type bar, and means controlled by the movement of said fly weight for operating said means for effectively uncoupling saidtype bar from said drive means.

10. In a typeaction having a power roll, a type bar. means for effectively coupling said type bar to said power roll, and means decelerating said trpe bar during free flight of the latter, the free flight speeds of said type bar required at positions located diiferent distances from the printing point to give a predetermined intensity of printing impact against the action of said decelerating means being known; the improvement comprising means for effectively uncoupling said type bar from said power roll, means for sensing the arrival of said type bar at a dynamic condition of speed and position which corresponds to one of the said known conditions, required for giving the said desired type bar impact, and means responsive to the oper" ation of said sensing means for operating said means for efiectively uncoupling said type bar from said power roll.

11. Apparatus as defined by claim 10 wherein said sensing means includes a centrifugally sensitive fiy weight yieldably connected for timed swinging movement with said type bar, and a bail tooth having an operative surface predeterminedcontour and position respect to the center of the swinging movement of said fly weight and adapted to be engaged at various spoints bysaid fly weight. t 7

References Cited in the file of this patent UNITED STATES PATENTS Q 2,314,677 Young Mar. 23, 1943 2,856,052 Luhn Oct. 14, 1958 2,861,669

Letterman .c -Nov. 25, 1958 

